1. Field of the Invention
This invention relates to variable ratio brake pedal mechanisms which during initial movement of the brake pedal in a brake applying stroke operate with a high ratio of movement of the brake actuator relative to movement of the brake pedal and in the last part of the stroke operate with a low ratio between the same parts.
2. Description of the Prior Art
It is desirable to shorten the stroke or amount of movement of the pedal which is used to apply the brakes of motor vehicles, including highway vehicles and also larger off-the-road vehicles, and some users of such vehicles place limits on the amount of such pedal movement. A brake pedal with a short stroke has the advantages that the brakes can be applied more quickly and with a smaller amount of pedal movement by the operator.
In a typical hydraulic brake system there is lost motion in that most of the stroke of the brake pedal is required to fill up the brake hydraulic system from the master cylinder. The last part of the stroke of the brake pedal is utilized to pressurize the system and actually apply the brakes.
Prior patents have disclosed mechanisms intended to deal with the same problem, such as U.S. Pat. Nos. 1,754,354; 2,315,632; and 3,678,779. These patents and others utilize cams either separately or in conjunction with levers in variable ratio brake mechanisms.
It is known also to use toggle linkages in brake pedal mechanisms and examples of such linkages are disclosed in the U.S. Pat. Nos. 2,884,803 and 3,142,199.